1. Field
One or more embodiments of the present disclosure relate to an electronic apparatus capable of measuring an actual exposure time of a shutter unit.
2. Related Art
Lately, digital single-lens reflex (DSLR) cameras, which enable expert-level photography, are coming into wide use.
In a DSLR camera, which sends the image of an object to a viewfinder, and sends light to an imaging device for taking a picture through a single lens, a focal plane shutter is positioned in front of the imaging device to regulate the exposure time of the imaging device. The focal plane shutter is a mechanical shutter including two curtains called a front curtain and a rear curtain. The front curtain and the rear curtain travel left and right or up and down at an input shutter speed, and exposure is made through a gap between the front curtain and the rear curtain. The front curtain travels first, and the rear curtain travels in succession according to a set exposure time. During an exposure time until the rear curtain completely covers the imaging device, an image is recorded by the imaging device. The travel of the front curtain and the rear curtain is caused by elastic force of a mechanical connection, and is started by stopping application of current to an electromagnet connected to the front curtain and the rear curtain.
The shutter speed of the focal plane shutter is limited to a maximum of 1/300 sec. A digital technique of time-divisionally receiving respective amounts of light through the gap between the front curtain and the rear curtain while the focal plane shutter travels, and then generating an output image by joining divided images together has increased the maximum shutter speed up to 1/8000 sec. However, the divided images recorded in this way are not recorded from one scene with the same exposure. Therefore, when an object moves at a high speed, or in a situation with rapidly changing exposure such as instantaneous light, part-specific exposures may cause a separated area in an output image, or limit the highest shutter speed when divided images of strobe photography using instantaneous light are synchronized.
To overcome such limitations, it is necessary to remarkably increase the travel speed of the front curtain and the rear curtain of the focal plane shutter and set the gap between the front curtain and the rear curtain to be narrow. However, it is difficult for the travel of the front curtain and the rear curtain having mechanical structures to coincide completely with high-speed travel as described above, and there is a desire for a control method which complements the travel.